George Bidder and Zerah Colburn (an American), who exhibited publicly.

3

Inaudi exhibited his astounding powers of calculatin at Paris in 1880, his additions and subtractions were from left to right.

4

Buxton, being asked How many cubical eighths-of-an-inch there are in a body whose three sides are 23,145,786 yards, 5,642,732 yards, and 54,965 yards? replied correctly without setting down a figure.

Colburn, being asked the square root of 106,929 and the cube root 268,336,125, replied before the audience had set the figures down.Price: Parallet History, vol. ii. p. 570.